I think that's cool. The Scent of Lotus, however, should be like this:

Scent of Lotus, 4
Legendary Artifact
tap, reveal any number of spells. Add X mana to your mana pool, where X is the number of lands revealed this way. Mana added this way can only be of the color of the revealed cards.

Flickering Powerstone 1
Artifact
T: Add 2 to your mana pool.
3: Untap Flickering Powerstone. This ability may only be played once per turn

With that last added sentance if it where to be targeted by Power Artifact, then it could only be untapped once. This way it is also vulnerable to Disenchants and Capsizes. Also it is targetable by the Voltaic Key wich would not coun't against the second ability of being used once. This will cut down on its abuse power. Hope this Idea works.

Mana Rig
4
Artifact
As long as Mana Rig is untapped, players may play artifact spells whenever instants would be legal.
At the beginning of your upkeep, tap Mana Rig unless you sacrifice a non-creature artifact.
"Six blue mana? And a killer drawback? Good heavens, the ability isn't that great."

I have NO idea what instant artifacts has to do with the Mana Rig, which produced powerstones. A real Mana Rig should produce Mana Vault Tokens.
======Lotus Grinder(formerly Scent of Lotus)
2
Artifact
Lotus Grinder comes into play tapped.
Tap, Sacrifice Lotus Grinder: Reveal and number of land cards in your hand. Add X mana of any one color to your mana pool, where X is the number of land cards revealed.
"Coming into play tapped still does not guarantee that I'm not broken."
======
I like Istanbul's version of the mana artifact the best.
======
Comments?

Cateran Overlord 3BBBBB
Creature-Mercenary Legend
First Strike
Cannot be the target of controller's spells or effects.
Sacrifice a Creature: Regenerate Cateran Overlord
Pay 3 Life: Pro White until end of turn.
Sacrifice a creature: Pro Green until end of turn.
XBBB: Search for a Mercenary converted mana cost X or less and so on...
When Cateran Overlord is put into the graveyard from play, sacrifice 4 other Mercenaries. If you cannot, lose 10 life.
7/7
"Not even the Magistrate in his lofty tower is out of our reach."

God I love overpowering creatures
This is just a random musing on me, I'll be back soon enough with some ideas

Xterra, Keeper of the Crypt-3RR
Creature-Minion
*/*
Xterra, Keeper of the Crypt has power and toughness equal to the number of lands in all graveyards.
When Xterra, Keeper of the Crypt comes into play sacrifice all but 3 lands you control.

Crovax, Evincar of Rath 3BBB
Creature - Vampire Legend
4/3
Flying
BB: Crovax gets +1/+1 until end of turn.
If any creature is placed into any graveyard on the same turn as Crovax, Evincar of Rath damaged it, remove it from the game and put a +1/+1 counter on Crovax, Evincar of Rath.

- Crovax has become godlike. Makes Volrath look like Pee-Wee Herman. The removal from game thing is because Crovax doesn't just kill you, he eats your lifeforce. There's no 'you' to resurrect anymore. The Sengir effect is PERFECT for Crovax; it specifically says that the more lifeforce he eats, the stronger he gets. And I gave him half the ability of a Frozen Shade. (Note that pumping him up costs the same amount of mana as casting Vicious Hunger.)

I know, he's really strong, but Crovax IS really strong. I also made him legendary.

Everlasting Dragon-5RRR
6/9
Flying
RRRReal 5 Damage to target creature or player, this ability may only be used once each turn.
"Try to stop me, you can't"
------------------------------------------------------------

Nightstalker-2B
*/*
First Strike
Nightstalker has power and toughness each equal to the number of creatures in your graveyard.
"Lhurgoyf here I come"
------------------------------------------------------------

Power Helix-5
Creatures you control cannot be the target of spells or abilities.
Power Helix may not be the target of spells or abilities.

Chaos, lemme know what you think...and also take a look at my other cards.

Ok, first of all.....Have you ever hear of an Elvish Archer...same thing as the Lightning Spirit except it has First strike instead of flying....or maybe you've heard of Thunder Spirit....for just 1 more W this guy is a 2/2, Flyer with first strike....so how is my cards broken.

Maybe the Dragon is broken so how about making it cast to a 8RRRR....no matter what it's casting cost, people would still put this puppy in a sneak attack deck. Maybe make the ability cost RRRRR instead.

Oh...and the Lhurgoyf on crack....how is this guy BROKEN....Lhurgoyf costs 2GG and has P/T equal to all the creatures in all graveyards....I don't understand your logic....also doesn't the Lhurgoyf have Trample, yeah he has First Strike, but I would rather have Trample then have First strike.

And lastly....the Helix....I don't see how this card is broken....maybe have it cast to a 6...but I don't see many decks that would run this card.

If you wanna explain your logic then you may, but don't just sit there and criticize my cards.

Don't post cards here if you don't want people to give you their honest opinions.

Yes, I've heard of Thunder Spirit, 1WW for a 2/2 flying first striker. It was broken, too. White generally pays 2W for the average 2/2 creature. (Pearled Unicorn) 1WW for a 2/2 with flying OR first strike is generous, but doable. Both is simply broken, and deducting 1 from the toughness isn't enough to reduce the casting cost to 1W.

The Helix is broken because it renders over a hundred cards completely impotent. Not only can you no longer Boomerang, Arrest, Pacify, Desert Twister, Bolt, Drain, Vendetta, Shock, or otherwise use any direct method of dealing with creatures, but this card specifically keeps itself in play. Nothing short of non-targeting artifact destruction will remove this overpowering card from play, and there have...um...let's see. Purify, yeah, that sees a LOT of play...green has nothing...blue has nothing...red has Shatterstorm, a sideboard card...black has nothing. Oh yeah. That's fair.

Lhurgoyf isn't broken because if there are only, say, 4 cards in graveyards, a 4/4 trampler isn't that hard to handle. But a 4/4 first-striker can easily rule the board, and he makes himself bigger every time he eats one of your opponent's creatures. It doesn't help that you made him cost LESS than his counterpart, and put him in a color where he'd be immune to 90% of black's removal.

Everlasting Dragon is one of those broken-at-any-price cards. To make him cost enough to where being able to ping for FIVE DAMAGE EVERY TURN would be fair, he'd have to be incredibly, prohibitively expensive. And quite frankly, I'm not too thrilled about making a card that would only ever be used in a deck that never should have been made in the first place. (The first time I saw Sneak Attack, I traded it away low, because I thought I was somehow reading it wrong. It couldn't possibly let you cast any creature for R and turn that creature into a Ball Lightning...or maybe it could.) Actually, let's calculate our little friend's mana cost.
Red pays 3R for a 3/3, a Hill Giant.
Add +3/+3, add 3, making it a 6/6 for 6R.
Give it flying (out-of-theme for red), add R.
Give it the ability to do direct damage, add R.
What we end up with is a 6/6 (not a 6/9) that does direct damage and flies, for 6RRR. (If you'll note, that's not too far away from what a Shivan Hellkite costs.)

And finally...if you don't want people to tell you what they think, don't tell them what you think. Folks like to reciprocate.

I didn't THINK it did, but I was willing to give XDanish the benefit of the doubt. So now we're paying less for a creature that gains first strike (a very potent ability on a large creature) that's in a color that not only excels in putting creatures in the graveyard, but is immune to 90% of black removal. Oh yeah. That's good.